/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * libc/stdlib/lib_qsort.c
 *
 *   Copyright (C) 2007, 2009, 2011 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Leveraged from:
 *
 *  Copyright (c) 1992, 1993
 *  The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by the University of
 *    California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <sys/types.h>
#include <stdlib.h>

/****************************************************************************
 * Preprocessor Definitions
 ****************************************************************************/

#define min(a, b)  (a) < (b) ? a : b

#define swapcode(TYPE, parmi, parmj, n) \
	do { \
		long i = (n) / sizeof(TYPE); \
		register TYPE *pi = (TYPE *)(parmi); \
		register TYPE *pj = (TYPE *)(parmj); \
		do { \
			register TYPE  t = *pi; \
			*pi++ = *pj; \
			*pj++ = t; \
		} while (--i > 0); \
	} while (0)

#define SWAPINIT(a, size) \
	swaptype = ((char *)a - (char *)0) % sizeof(long) || \
	size % sizeof(long) ? 2 : size == sizeof(long) ? 0 : 1;

#define swap(a, b) \
	if (swaptype == 0) { \
		long t = *(long *)(a); \
		*(long *)(a) = *(long *)(b); \
		*(long *)(b) = t; \
	} else { \
		swapfunc(a, b, size, swaptype); \
	}

#define vecswap(a, b, n) if ((n) > 0) swapfunc(a, b, n, swaptype)

/****************************************************************************
 * Private Function Prototypes
 ****************************************************************************/

static inline void swapfunc(char *a, char *b, int n, int swaptype);
static inline char *med3(char *a, char *b, char *c, int (*compar)(const void *, const void *));

/****************************************************************************
 * Private Functions
 ****************************************************************************/

static inline void swapfunc(char *a, char *b, int n, int swaptype)
{
	if (swaptype <= 1) {
		swapcode(long, a, b, n);
	} else {
		swapcode(char, a, b, n);
	}
}
static inline char *med3(char *a, char *b, char *c, int (*compar)(const void *, const void *))
{
	return compar(a, b) < 0 ? (compar(b, c) < 0 ? b : (compar(a, c) < 0 ? c : a))
		   : (compar(b, c) > 0 ? b : (compar(a, c) < 0 ? a : c));
}

/****************************************************************************
 * Public Function
 ****************************************************************************/

/****************************************************************************
 * Name: qsort
 *
 * Description:
 *   Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
 *
 ****************************************************************************/

void qsort(void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *))
{
	char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
	int d, r, swaptype, swap_cnt;

loop:
	SWAPINIT(base, size);
	swap_cnt = 0;
	if (nmemb < 7) {
		for (pm = (char *)base + size; pm < (char *)base + nmemb * size; pm += size) {
			for (pl = pm; pl > (char *)base && compar(pl - size, pl) > 0; pl -= size) {
				swap(pl, pl - size);
			}
		}
		return;
	}

	pm = (char *)base + (nmemb / 2) * size;
	if (nmemb > 7) {
		pl = base;
		pn = (char *)base + (nmemb - 1) * size;
		if (nmemb > 40) {
			d = (nmemb / 8) * size;
			pl = med3(pl, pl + d, pl + 2 * d, compar);
			pm = med3(pm - d, pm, pm + d, compar);
			pn = med3(pn - 2 * d, pn - d, pn, compar);
		}
		pm = med3(pl, pm, pn, compar);
	}
	swap(base, pm);
	pa = pb = (char *)base + size;

	pc = pd = (char *)base + (nmemb - 1) * size;
	for (;;) {
		while (pb <= pc && (r = compar(pb, base)) <= 0) {
			if (r == 0) {
				swap_cnt = 1;
				swap(pa, pb);
				pa += size;
			}
			pb += size;
		}
		while (pb <= pc && (r = compar(pc, base)) >= 0) {
			if (r == 0) {
				swap_cnt = 1;
				swap(pc, pd);
				pd -= size;
			}
			pc -= size;
		}

		if (pb > pc) {
			break;
		}

		swap(pb, pc);
		swap_cnt = 1;
		pb += size;
		pc -= size;
	}

	if (swap_cnt == 0) {
		/* Switch to insertion sort */

		for (pm = (char *)base + size; pm < (char *)base + nmemb * size; pm += size) {
			for (pl = pm; pl > (char *)base && compar(pl - size, pl) > 0; pl -= size) {
				swap(pl, pl - size);
			}
		}

		return;
	}

	pn = (char *)base + nmemb * size;
	r = min(pa - (char *)base, pb - pa);
	vecswap(base, pb - r, r);
	r = min(pd - pc, pn - pd - size);
	vecswap(pb, pn - r, r);

	if ((r = pb - pa) > size) {
		qsort(base, r / size, size, compar);
	}

	if ((r = pd - pc) > size) {
		/* Iterate rather than recurse to save stack space */

		base = pn - r;
		nmemb = r / size;
		goto loop;
	}
}
